PIGS DON’T SWEATMost of us spend a lot of time and energy training every year for a summer triathlon. When the race finally arrives, it may not be the cold water swim, the wind in your face during the bike ride or the hilly run that is the biggest obstacle to a successful race. Triathlons are usually held in hot weather to allow for warmer water conditions. Thus, the toughest element of the event may not be the swim, bike or run but the survival of high temperatures and humidity. Any time that work is performed, whether it is by your car engine or by your muscles, heat is generated. Seventy percent of the energy produced by exercise becomes heat. The rest is productive work. If none of the heat is carried away, the human body temperature will rise one degree every five minutes. When body temperature reaches 106 degrees Fahrenheit, most of us will suffer convulsions. The final heat load is the resultant balance between the amount of heat produced and the heat lost from the body. We must have ways to get rid of heat to avoid heat injury. Humans have several avenues from which to expel heat onto the external environment. These are
Radiation is the process by which an object emits heat in the form of electromagnetic waves. If a temperature difference exists between two objects, the warmer object will transfer heat onto the cooler object. A good example is the sun. It is a powerful radiator that emits heat onto anything in its path of light. Homes built in the early 50’s were heated by hot water radiators. Conduction is the transfer of heat by direct contact with a cooler surface. This avenue of heat dissipation is limited in sports, since we are usually moving. It would not be much of a race if we were sitting on a block of ice. A larger temperature difference results in more heat transferred. Convection is heat transfer onto moving air or water. Air or water which passes over the skin picks up heat and is replaced by cooler air or water. Natural wind or that produced by movement such as bicycling further facilitates heat loss. In cold weather, this is commonly referred to as the wind-chill factor. Despite the aforementioned ways to dispel heat, the cooling effect is limited if the temperature is above 80 degrees and humidity is high. Most members of the animal world do not have as many options to dissipate heat generated during heavy exertion as humans do. Humans possess relatively hairless skin, an efficient cardiovascular system, and most importantly, advantage in the ability to sweat profusely. In the animal kingdom we are considered homeothermic because we are able to maintain our body temperature within a narrow range. Water evaporation from sweat provides effective heat loss, even in hot environments. Humans have 2 to 4 million sweat glands which are capable of producing 2 to 4 liters of sweat per hour. When sweat transforms from a liquid state to a gas (evaporation) heat is lost. Sweat must evaporate to exert its cooling effect, sweat that rolls off your skin is ineffective. High humidity which represents high water vapor concentration in the air, compromises the extent of evaporation. Most other mammals lack sweat glands. Evaporative losses by dogs are limited to panting moisture from their lungs and licking moisture onto their fur. Pigs do not sweat but cool themselves by rolling in mud. The price we pay for sweat is dehydration and resultant strain on the cardiovascular system. With sufficient water replenishment, human beings can tolerate heat challenges for long periods of time which would be lethal to our furry friends. Athletes vary in the amount of sweat loss under similar conditions. The best way to estimate your fluid replacement needs is to weigh yourself before and after a workout. A pound of body weight loss equals a pint of water. Add to your observed weight loss the amount of water consumed. The total figure is your water needs to maintain hydration. This will provide you with a guide as to how much to drink per hour under similar conditions. In a race such as a 10 to 13 hour Hawaiian Ironman triathlon, proper hydration is the key to a good performance. A noted example of sweat loss occurred when Alberto Salazar ran the 1984 Los Angeles Olympic Marathon. In this race he lost 12 pounds of body weight. His finish time was 2 hours and 12 minutes. This calculates to 1 pint of sweat loss every 11 minutes. Northwesterners do not have to compete in Hawaii to encounter hot conditions. Events such as the Whiskey Dick Triathlon, Troika Triathlon, and Ironman Canada are examples of hot weather events in our local race schedules. One of the Seattle to Portland bicycle rides in the late 80’s was complicated by temperatures in the low 90’s. The next time, someone says to you " you’re sweating like a pig", you are not breaking a sweat. Remember sweat is our friend. Drink a lot and follow a motto used annually at the Ironman "Drink until your urine is clear and copious". QBullets are used in this site. QBullets
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